Wasn't sure whether this shoudl go in LT1 tech or the programming forum. Sorry if I'm in the wrong place.

Because of cam overlap my O2s are reading too much air at idle and causing me to run REALLY rich in closed loop. Under acceleration and cruising however it seems to do great...but my idle in closed loop is just too rich and also really rough.

So I'm debating going to an open loop tune to ignore the O2s entirely. I've read some debate on doing this though on cars with cats becuase you will ruin the cats if the mixture gets to rich (and the computer won't know it without the O2s). However at the current time my car is running so rich at idle i'm concerned with that frying my O2s as well (especially in city driving). So my thinking seems to tell me that just ignoring the O2s is going to giv eme a much better A/F ratio at idle. On top of that, assuming my MAF sensor is working fine evne under acceleration/cruising shouldn't my A/F ratio remain pretty accurate under an open loop system?

 

I currently do exactly what you're thinking of doing, and for the same reasons. My cats were actually glowing at idle. Fortunately I caught onto this before I ruined them. You may have to tweak the injector constant a bit to get the values in the open loop table anywhere near reality (I did). When I put 14.7 in some of the cells it was still too rich.

 

Oiriginally i had a PCMForless tune. Right now my injector constant is at 24.9 (still running stock injectors, won't know if i need bigger ones until the engine is broke in and i can open up the throttle). We'll see what happens. Out of curiosity what size injectors are you running and what did you end up setting your flow rate to?

 

I forgot to mention I'm using 36lb SVO (Bosch) injectors with the FP turned up. So obviously the stock values wouldn't even run the engine. Currently it's at 45.6. BTW the engine doesn't care if the numbers in the OL table are the real AFR's, but I wanted them to be accurate to facilitate future tweaking.

 

I assumed you used a wideband sensor to setup your tune and get the A/F ratio right then? I might need to look into at least getting a tail pipe sniffer, bt that's not gunna help me tune WOT values, i'd need to be on a dyno i guess.

 

do you have tuner cat if so i can help you. you dont need a open loop tune. there are other ways to fix it did one today.

if you have tunercat send me your bin file vincentbergeron@yahoo.com

 

by the way if your not really experianced in tuning and not sure waht to watch, the open loop tune can be very dangerous. and if you drive to long with it running real rich you will wash the cylinder wall and run the engine.

so it need to be addressed asap.

 

I'm at work now and don't have the .bin file handy. I was just reading the whole closed loop idle discussion under the programming forum. It seems like most feel it can't be accomplished. I'm unclear when you say i could wash my engine though. The onyl way i see that happeniny is if the MAF went bye bye and the engine thought it was getting more air than it really is and dumping fuel. Outside of that the A/F ratio will be based off the MAF reading alone, right?

edit: yah, i have tunercat.

 

no everybdy pretty much agrees it can be done. the process it what is being discused. you have to use the blm locker along with the tune.

now the "wash" term....ok if your running rich, truely rich...anything below a blm of 108. this means your pcm cannot take out enough fuel to compensate for the rich condition. ok now if you tell the pcm you 24 lb# injector and you have 36#, the o2s will pick up the exrta fuel to a extent and lean the mixture out by lowering the pulse width. but its lowering it, thinking it has 24# when it has 26# now you have this un godly rich condition that the pcm has corrected as much for as possible. and you dumping so much fuel that it washing the oil off the cylinder walls and it will ruin the rings and eventually the motor.

and the maf is not the olny thing that controls the fuel. the injector constants, the cylinder fuel trim, and also the previous blms the monent you go wot play a role it the tageted fuel ratio of power enrichment mode (or better known as wot.

im tellin you it can be dangerous to eun a open loop tune.

 

The other day I noticed in tunercat in the constants there is a place to provide an MPH requirement to go into closed loop, does that do anything at all? IS there a way to keep the engine in open loop while under say 1200 RPMs?

 

the only way i tunercat to keep the pcm in open loop is by temp. dont see anythng in the costants for mph open loop.



and yes

 

That would seem to be the best solution is keep it in open loop under 1200 RPMs. The engine runs fine in closed loop once i'm cruising/accelerating it's just idle.

 

what lsa is the cam on.

 

112 Lsa